Calculating Heat Over a Cycle: Q, dU, W

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SUMMARY

The discussion focuses on calculating heat transfer over a thermodynamic cycle using the equation Q = ΔU + W. Participants clarify that heat is added during the forward processes (a-b and b-c) and expelled during the reverse processes (c-d and d-a). The equation Q = nCvdT + pdV is specifically mentioned for calculating heat expelled from process d to a. Understanding the relationship between temperature changes and work done is essential for accurate calculations.

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Homework Statement



How much heat is added over this cycle? During which processes?
What is the heat expelled from d to a?

Homework Equations



http://img838.imageshack.us/img838/6270/29494670.png
(Goes clockwise, abcda)

The Attempt at a Solution



I'm just generally confused overall about this question. Is heat added in the processes which are going "forward"? So would heat only be added during processes a-b and b-c?

And would I use Q = dU + W to calculate the heat added for the processes?

For the 2nd question, for heat expelled, would I still just use Q = dU + W to find it?
So Q = nCvdT + pdV to find the heat expelled for process d to a.

Thanks for any clarification and help, I am really lost here.
 
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Anyone?
 
Hi. Yes, you would use Q = ΔU + W to get the heat added or expelled for each path segment. Q is positive for heat added, and negative when heat is expelled.
 
How does the temperature at c compare to the temperature at b? Use that to determine the heat flow from b-c.

How is the net work done by the system related to the heat in and heat out?

AM
 

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